NMR Spectrum of Malathion & Xylene

Malathion

This spectrum contains signals from ethyl ester and keto-alkyl groups, and a signal from two methoxy groups on the phosphorothioyl functional group. Asymmetry of the butanedioate chains allows differentiation of multiplicity of the two ethyl signal groups. Heteronuclear coupling, 1H{31P}, of the terminal methoxy protons on the phosphorothioyl to 31P, a spin ½ nucleus, is evident in the spitting of the terminal methyl into a doublet. The measured 31P-1H coupling constant, 3JPH, is 15.2 Hz and agrees well with published values.

High resolution 82 MHz spectra of organophosphate compounds acquired with the picoSpin 80 1H NMR spectrometer reveal subtle differences in molecular geometry and indirect detection of hetero nuclei, demonstrating the capacity of benchtop NMR to provide a wealth of structural information in a small, dilute sample volume. Sample preparation, testing and verification of raw chemicals on the receiving floor, or analysis of organophosphate solutions at the bench are examples of quick and easy applications of bench top NMR, providing both timely and complex spectral data.

Malathion’s main application is for controlling or eradicating mosquito populations, but is also effective against fruit fly populations. It is one of several insecticides used in cities in combat against mosquito species carrying the West Niles virus. It is used in agriculture and residential landscaping, and in public recreation areas. In low concentrations, Malathion is also used as a treatment for head and body lice, and as an alternative treatment for Scabies, a contagious skin infection caused by the itch mite Sarcoptes scabiei. In insects, Malathion works by binding irreversibly to an enzyme produced in the nervous system that transmits signals between nerves, thus overwhelming nerves with signals resulting in death.

Xylene

This spectrum contains signals from all there xylene isomers and the ethylbenzene impurity. Each isomer of xylene produces a slightly different 1H NMR spectrum. The highly symmetric p-xylene produces two signals, one aliphatic signal due to the substituent methyl protons, and a second aromatic proton signal. The lower symmetry o-xylene and p-xylene molecules produce complex aromatic signals that overlap and are indistinguishable. However, the methyl signals have slightly different chemical shifts allowing one to differentiate the para from the ortho and meta isomers. Ethylbenzene is indicated in this picoSpin 45 spectrum as an impurity and is easily recognizable by its characteristic multiplet pattern.

With the picoSpin 451H NMR spectrometer one can test a variety of solvents, chemical precursors and bench chemicals easily and rapidly, providing timely data for analysis of common chemicals in the lab, on the bench top where the chemistry occurs. Liquid samples, like xylene, can be sampled and injected into the spectrometer as pure liquids without the need for dilution, making testing quick and uncomplicated.

Xylene’s main applications are as a precursor in the production of the monomers terephthalic acid and dimethyl terephthalate that are used to make polyethylene terephthalate (PET) plastic bottles and polyesters. It is also used as a solvent and cleaning agent in a variety of industries, such as the printing and leather industries, and as has general application in thinning paints and varnishes, as a cleaning agent for electronics and silicon wafers, and as a solvent in dentistry. Its uses in the chemistry lab are as a solvent and cleaning agent of oils, grease and waxes. Individual isomers of xylene when mixed with dry ice produce a wide range of cooling bath temperatures, from +12 °C for p-xylene/dry ice to -47 °C for m-Xylene/dry ice, which are used for cooling reaction vessels.

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